The present invention relates to a device for the determination of tissue perfusion in applications in which the wearing of safety glasses would constitute a hindrance, and the operative use of such a device.
A device and process for angiofluorography of the skin are described in xe2x80x9cMicrovascular Researchxe2x80x9d 1994, Vol. 47, pp. 240-251. In this case, after application of indocynanin green, the blood circulation through the skin is assessed on the basis of the fluorescence signal, which occurs as a result of excitation by means of radiation in the near-infrared range. There serves as radiation source here a 2000 watt halogen lamp with a bandpass filter connected in front of it as well as a water filter necessary because of high heat development. A CCD camera serves as detector.
A device and process for examining burns by means of fluorescence measurements after application of an exogenous chromophore are disclosed in U.S. Pat. No. 5,074,306. The imaging apparatus consists of a xenon or mercury vapour lamp as excitation light source, an intensified CCD camera and a computer with image processing software.
If halogen or mercury vapour lamps are used as light sources for excitation of the chromophore, then these must have a relatively high power, as only a short wavelength range of the broad-band radiation is usable for fluorescence excitation, and the rest of the generated light must be filtered out by means of a bandpass filter. The necessary high lamp power in the kilowatt range results in correspondingly high heat generation, which requires cooling measures, and also in a large structure in particular of the electrical components.
Portable, mains-independent configurations are therefore not possible with such light sources.
A device and process for measuring the blood circulation through transferred skin grafts, wherein after application of indocyanin green the fluorescence excited by radiation with a pulsed laser array is detected with a CCD camera, are known from xe2x80x9cAnnals of Plastic Surgeryxe2x80x9d 1999, Vol. 42, pp. 266-274.
A device and process for tumour detection in animal tissue, wherein after application of indocyanin green the fluorescence excited by radiation with a pulsed laser diode is detected with a CCD camera, are described in xe2x80x9cPhotochemistry and Photobiologyxe2x80x9d 1999, 70(1), pp. 87-94.
The use of appropriate laser light sources requires safety glasses to be worn when handling the systems and also requires that the rooms in which they are applied are identified for safety reasons. This is not a significant problem for purely diagnostic tasks, but renders such systems unsuitable for operative application, since special laser protection measures would have a disruptive effect in routine surgical use.
A device for infrared video angiography of the fundus of the eye, which has a near-infrared light source for the excitation of fluorescence of indocyanin green as well as a detector camera, is disclosed in U.S. Pat. No. 5,400,791.
However, the device disclosed in U.S. Pat. No. 5,400,791 is not suitable for operative observation of a larger operating area because of its design for ophthalmological diagnostics.
In view of the poor suitability of conventional diagnostic devices based on the fluorescence excitation of a chromophore for routine application in the operating theatre, the object forming the basis of the present invention is to provide a device for the operative determination of tissue perfusion, which is easy to handle, is also suitable for non-microinvasive procedures and in particular renders special protective measures such as the wearing of safety glasses superfluous.
Accordingly the present invention provides a device for the determination of tissue perfusion in applications in which the wearing of safety glasses would constitute a hindrance, said device including:
a radiation source, said source generating an electromagnetic bundle of rays in a wavelength range corresponding to the wavelength range of the fluorescence excitation of a chromophore;
an optical expansion unit;
a safety housing; and
an electronic camera with an optical filter, said filter being transparent to emitted light of the excited chromophore and opaque to the wavelength range of said generated bundle of rays;
wherein said radiation source and said optical expansion unit are integrated into said safety housing whereby only an expanded bundle of rays with an intensity not exceeding a limit value that excludes any risk to persons present in the vicinity of the device, can emerge from said safety housing, and said optical expansion unit enables the illumination of an operating area sufficiently large for non-microinvasive procedures.
The present invention also provides a method of using the above device for the determination of tissue perfusion, wherein the determination occurs operatively, i.e. during a surgical operation.